Olefin terpolymerizations. III. Symmetry, sterics, and monomer structure in ansa‐zirconocenium catalysis of EPDM synthesis

Ethylenebis (η5‐fluorenyl) zirconium dichloride (1) and rac‐dimethylsilylene bis (1‐η5‐in‐denyl) zirconium dichloride (2) were activated with methylaluminoxane (MAO) to catalyze ethylene (E) propylene (P) copolymerizations. The former produces high MW copolymer at 20°C rich in ethylene with reactivity ratio values of rE = 1.7 and rP <0.01, whereas the latter produces lower MW random copolymers with rE = 1.32 and rp = 0.36. Ethylidene norbornene (ENB) complexes with 1/MAO but does not undergo insertion in the presence of E and P. In contrast, 2/MAO catalyzes terpolymerization incorporating 9‐15 mol % of ENB with slightly lower MW and activity than the corresponding copolymerizations. In comparison, 1,4–hexadiene was incorporated by 2/MAO with much lower A and MW. Terpolymerizations were also conducted with vinylcyclohexene using both catalyst systems. The steric and electronic effects in these processes were discussed.